This invention relates to an internal combustion engine and particularly to a direct injected internal combustion engine provided with a supercharger.
It has been proposed to employ direct cylinder injection for internal combustion engines. By utilizing direct injection, it is possible to operate the engine more efficiently and also to obtain greater power and still improve the efficiency. This can be done by achieving a condition referred to as xe2x80x9cstratificationxe2x80x9d in the engine under some running conditions, normally lower speed and lower load conditions.
As the performance of the engine is improved, however, it may be difficult for the direct injector to supply not only the minute quantities of fuel required under very low speed, low load conditions as well as the larger quantity of fuel necessary to obtain maximum power output. Although this can be done by providing injectors that have a higher capacity, then the ability to inject controlled small amounts of fuel under low load conditions becomes very difficult. Also, if the injection is set so as to provide adequate and carefully controlled small amounts of fuel, then fuel must be injected for a longer time period under high speed and high load conditions and this can result in unwanted exhaust gas constituents because of the fact that the fuel may not have had the time to vaporize before combustion starts.
These problems are particularly prevalent when the engine has its power increased through the use of a supercharger or pressure-forming device for introducing the charge into the combustion chamber at pressures greater than atmospheric.
It is, therefore, a principal object to this invention to provide an improved fuel injection system for a direct injected engine that permits accurate fuel control over a wide speed of engine load and speed ranges.
It is a further object to this invention to provide an improved fuel injection system for a supercharged internal combustion engine.
An internal combustion engine constructed in accordance with an embodiment of the invention is provided with a pair of relatively moveable components that define a combustion chamber, the volume of which varies cyclically during the engine operation. An induction system is provided for delivering an air charge to the combustion chamber. A first fuel injector is provided that injects fuel directly into the combustion chamber. A second fuel injector is provided for injecting fuel into an induction system that supplies an air charge to the combustion chamber. A control selectively controls the timing and duration of fuel injection from both of the fuel injectors.
In accordance with a further feature of the invention, the engine is provided with a supercharger which is mounted upstream of the second fuel injector.